Hood post crane



March 20, 1962 H. L. MCFEATERSQ HOOD POST CRANE l6 Sheets-Sheet 1 FiledMarch 18, 1958 RAMP. DOW/V RAMP- aanw l J rlllL March 1952 H. L.MOFEATERS 3,025,102

HOOD POST CRANE Filed March 18, 1958 16 Sheets-Sheet 2 March 20, 1962 H.L. MCFEATERS HOOD POST CRANE l6 Sheets-Sheet 5 Filed March 8, 8

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March 20, 1962 H. L. MGFEATERS HOOD POST CRANE 16 Sheets$heet 8 FiledMarch 18, 1958 March 20, 1962 H. L. M FEATERS 3,026,102

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16 Sheets-Sheet 11 H. L. M FEATERS HOOD POST CRANE March 20, 1962 FiledMarch 18, 1958 RE M, o QH March 20, 1962 Filed March 18, 1958 H. L. MFEATERS 1-1001) POST CRANE 16 Sheets-Sheet 12 IVA/W?! L MCFEA TERS HIS ATTORNEVS' March 20, 1962 H. L. MCFEATERS HOOD POST CRANE 16 Sheets-Sheet14 Filed March 18, 1958 INVENTOR.

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HOOD POST CRANE Filed March 18, 1958 16 Sheets-Sheet 15 INVENTOR. 644m?Y L Mc F124 TERS il izcm w HIS A77'OR/VE'VS.

March 20, 1962 H. MOFE'ATERS HOOD POST CRANE RN HN United States Patent6 3,026,102 HGOD POST CRANE Harr y L. Mcl eaters, New Castle, Pa.,assignor to Pennsylvania Engineering Corporation, New Castle, Pa., acorporation of Eennsylvania Filed Mar. 18, 1958, Ser. No. 722,257 26Claims. (Cl. 266-35) This invention pertains to a new and improvedoperating layout, system or procedure for a converter type of vessel orfurnace such as used in refining metal.

A phase of the invention deals with handling equipment to be used with avessel or converter for refining metal, such as steel, and forfacilitating the employment of such a vessel and increasing itsefiiciency and effectiveness of operation. Another phase deals with theprocessing and handling of hot, contaminant-laden discharges from themouth of a generator to avoid atmospheric contamination and recovermetal oxides, etc., that may be carried as fume, as dust particles or asvapor with the discharge. A further phase deals with apparatus forimproving the operation of a converter from the standpoint of theaspiration or air during the melting or refining operation.

As pointed out in my Patent No. 2,803,450, it is important to avoid thedirect discharge of fumes, flame and gas from a mouth of a vesseldirectly into the atmosphere, both from a standpoint of the well beingor" the community and from the standpoint of minimizing airplanespotting by night. The problem has become particularly important in viewof the increased acceptance of the socalled oxygen (LP) blow type ofrefining operation. Also, in such a type of operation, problems havearisen in connection with the employment of an overhead-introducedoxygen blow lance, its positioning and withdrawal, and in connectionwith the charging and pouring of the vessel, and with further chargingduring the melting operation, such as with slag-forming materialsincluding lime, mill scale, etc.

In providing a suitable apparatus and layout to meet the needs of suchan installation and provide a solution to the many problems involved,the factor or" space limitations has to be considered. In other words, Ihave found that the installation should be such that it can be adaptedto conventional mill space that may be available for conventional millinstallations which include overhead cranes. I have been able to developa construction and layout which can be installed for efiicient operationof one or more melting or converter vessels in substantially the samespace that has heretofore been allocated for open hearth and electricfurnace installations. Because of the need for raising and lowering ahood that is employed to collect the discharge from each vessel and forhandling the oxygen lance, the factor of head room space is particularlyimportant.

it should be noted that the discharge from a vessel, such as an oxygenblow vessel or converter, may be within a temperature range in theneighborhood of about 3,000 to 3,l F. and particularly so, in connectionwith larger size vessels of, for example, 80 tons capacity or more.Thus, the apparatus employed should not only be able to withstand suchtemperatures with minimum maintenance, but should be capable of doing sowithout danger of explosions, and in such a manner as to fully take careof the large volume of the discharge, particularly during the blowingoperation, and in such a manner, that refining of the metal may beaccomplished with full and maximum efiiciency.

l have determined that overshadowing all the problems and factorsinvolved is the need for suitable supporting and handling apparatus, notonly for the hood, but also for the oxygen lance. It should be flexiblefrom the standpoint of individual reuuired operations as to the hood iceand lance and as to the conve ter, itself, and in such a manner that thelance may be cleaned and, if necessary, replaced as the need may arise.Although lances are water-cooled and when properly constructed will lastfor about to heats without cleaning, I have found that they Will lastfor about 1,000 heats when periodically cleaned. Atmospheric airnormally contains about 79% nitrogan, and the velocity of flow of anoxygen blow tends to aspirate the atmospheric gases into the mouth ofthe vessel. Thus, a much better refined product, closely approaching inquality that of the open hearth steel, may be attained by substantiallyeliminating the sucking-in of atmospheric gases.

In general, I have devised apparatus and an apparatus layout or systemthat meets the many factors and problems presented in this connection,that does so in a practical and eificient manner, and that permits anydesired usage of the converter vessel, including the additions of cleanscrap metal and of slag forming materials, and a proper charging andpouring of the vessel.

It has thus been an object of my invention to meet the factors and solvethe problems involved and to provide improved apparatus for cooperativeuse with a metal melting, refining vessel or converter;

Another object is to provide a system which will assure a new andimproved operative cooperation and functioning' between a vessel, a hoodand a lance;

Another object has been to provide a commercially practical embodimentof my inventive discoveries;

A further object has been to improve and facilitate the operation andthe resultant product produced by a converter melting type of metalrefining or conditioning process;

A still further object has been to provide improved apparatus forreceiving, controlling and processing the discharge from a convertervessel and for controlling and facilitating its operation;

These and other objects of my invention will appear to those skilled in'the art from my description of the illustrated embodiment thereof;

In the drawings, FIGURES 1a, 1b and 1c are plan views of a layout orsystem constructed and employed in accordance with my invention whereincentrally-disposed, slag-material-handling apparatus (see FIGURE 1b) isemployed with a pair of converter vessels and their attendant lance andhood apparatus;

More specifically, FIGURE 14 is a layout of a left hand convertersystem, FIGURE 1b is a plan of the centrally-disposed material-handlingsystem, and FIG- URE 1c is a plan of a right hand converter system thatis similar in construction, apparatus and operation to the system ofFIGURE 1a;

FIGURE 2 is an end view in elevation on the scale of FIGURES 1a, 1b and1c, showing a converter vessel in vertical operating position and itsrelationship with spark trap apparatus; a hood is shown in a raised andout-swung position with respect to the converter and the spark trapapparatus;

FIGURE 2a is a greatly enlarged sectional detail through the wall ofspark trap apparatus, such as illustrated in FIGURE 22, and showing atypical mounted relationship of cooling-fluid or water-spray means;

FIGURE 3a is a front or side view in elevation of the converter vessel,hood, spark trap apparatus, and of a ladle car of and on the same scaleas FIGURE 1a; it will be noted that the apparatus of 1c is of the sameconstruction as the apparatus of FIGURE la and thus, that FIGURE 3a isalso representative of the apparatus of FIGURE 10, except that it isturned FIGURE 3b is a side or front view in elevation on the same scaleas and taken along the line IIIbIIIb of FIGURE 1b;

FIGURE 4 is a view in elevation, taken along the line IVIV of FIGURE la,and on the same scale as that figure; it particularly illustrates mast,jib and swing frame features of post crane apparatus employed inaccordance with my invention; this view shows the general arrangement ofthe post mechanism;

FIGURE 5 is an enlarged horizontal section taken along the line V-V ofFIGURE 4, through the post crane apparatus;

FIGURE 6 is a fragmental section in elevation on the scale of and takenalong the line IV-IV of FIGURE 5;

FIGURE 7 is a plan detail of a swing arm or frame jib of a hood part ofthe post crane apparatus and on a slightly enlarged scale with respectto FIGURE la;

FIGURE 8 is a vertical fragmental view on the scale of FIGURE 7 andshowing outer portions of the hood jib of FIGURE 4, and particularlyshowing a swing jib hoist employed to change lances;

FIGURE 9 is a vertical view in elevation and partial section on thescale of FIGURES 7 and 8 and showing details of the construction ofoperating means for raising and lowering the hood frame;

FIGURE 10 is a somewhat diagrammatic or schematic view in elevationshowing support and hoisting means for a lance crane or jib of the postcrane apparatus and on the scale of FIGURES 1a, 1b, 1c and 4;

FIGURE 11 is an enlarged fragmental horizontal section, taken along theline XIXI of FIGURE 10;

FIGURE 12 is a fragmental vertical view on the scale of FIGURE 11 andtaken at right angles to FIGURES 10 and 11;

FIGURE 13 is a fragmental horizontal section on the scale of FIGURES 11and 12 and taken along the line )GIIXIII of FIGURE 12;

FIGURE 14 is an enlarged fragmental plan, partially in section,illustrating details of a pair of lance clamping means of which the lefthand one of this figure is carried by the hood jib and its swing arm,and the right hand one is carried by a fixed part of the post crane thatprojects outwardly as an arm or jib from the central part of the postcrane apparatus;

FIGURE 15 is a side view in elevation and partial section of thestructure of and on the same scale as FIG- URE 14;

FIGURE 16 is an enlarged plan view, partially in section, showingquick-coupling top connections to a head or closing cap part of thelance, whereby oxygen may be supplied centrally thereto, cooling fluidmay be supplied thereto about the oXygen-carrying portion, and heatedfluid may be removed therefrom;

FIGURE 17 is a side view in elevation and partial section on the samescale as and showing the structure of FIGURE 16;

FIGURE 18 is an enlarged side view in elevation and partial section,showing a converter vessel and its hood in a sealed or operatingposition with respect to each other, and illustrating details of theconstruction of the hood and of duct means for delivering additions,such as slag-forming materials, through the hood to the converter;

FIGURE 19 is a greatly enlarged fragmental plan view of aself-centering, sealing-off or lance gate means that is mounted on thehood to close or seal-0E a lance opening in the upper portion of thehood when the lance is in an operating position with respect to theconverter vessel; this figure is enlarged with respect to FIGURE 18;

FIGURE 20 is a view similar to FIGURE 19, but showing the gate means ina closed or sealed relationship about the lance, whereas FIGURE 19 showsit in an open relation, such that the lance top or head part may belowered or raised through the hood;

FIGURE 21 is a vertical view in partial section and on the same scale asand of the apparatus of FIGURE 20 and taken along the line XXIXXI ofFIGURE 20;

FIGURE 22 is a vertical view in elevation and partial section, on thescale of FIGURE 3a, showing the operating relationship between aconverter, its hood and spark trap apparatus, including exhaust piping;the spark trap apparatus, its construction, as well as its sludgecollecting means are illustrated in detail;

FIGURE 23 is an elevation in partial section on the same scale as and ofthe apparatus of and taken along the line XXIIIXXIII of FIGURE 22;

FIGURE 24 is a vertical view in elevation and partial section through aconverter, such as shown in FIGURES 1a and 10, which is adapted forutilization with the hood and other apparatus shown; this view is on ascale intermediate between FIGURES la and 18;

FIGURE 25 is a view in elevation taken at'right angles to and on thesame scale as the vessel of FIGURE 24;

FIGURE 26 is a top plan view of and on-the same scale as the vessel ofFIGURE 24;

And FIGURE 27 is a somewhat diagrammatic layout illustrating operatingconnections for cooling fluid, such as water, for oxygen supply "to thelance, and for pneumatic or pressure fluid to operate air motors orcylinders; this view also illustrates a so-called sight gravity feed ordrain of heated water or fluid that is returned centrally along the postcrane apparatus to the sewer or to a fluid reconditioning system.

The Operating Layout Referring particularly to FIGURES 1a, 1b and 10, Ihave shown a two unit converter installation or layout employing theprinciples of my invention. The converter vessels or metal-refiningunits A and their attendant apparatus are shown located at opposite endsof a centrally-disposed additive supply system that includes a car dumptrack hopper, grating unit or storage area 0, and an additive-supplyweighing and distribution unit or structure P. The unit P includesconveyors, elevators, weighing and discharge hoppers which may beemployed for supplying additives, such as mill scale and lime, tooppositely-disposed endwise-moving conveyors, one of which 225 suppliesadditives to the left hand converter and the other of which 213 suppliesthem to the right hand converter. Both of the converter vessels are ofthe same construction and are designated as A.

- Referring particularly to FIGURES la, is and 2, a post craneapparatus, structure or unit, designated as B, is 0peratively mountedfor movement between an out position I and an in or converter vesselcooperating position 11. As shown particularly in FIGURES 3a, 4 and 18,an inlet sealing ring or portion 114 of enclosing walls of a hood unit Dis adapted to make a sealing fit with a top lip or sealing edge 21a of amouth portion of the converter A when the post crane apparatus B is atposition II. It will be noted that the hood D provides a fumedischarge-receiving cover for the vessel A. At the same time, an outletsealing flange portion 119 (see FIGURES 2, 3a, 18 and 22) of theconverter A makes a sealing abutment with an inlet sealing face flangeportion 141 of a fume processing receiver or spark trap apparatus G. Itwill be noted that the hood D (see FIGURE 3a) is shown of relativelyshort length to provide a direct flow path between the vessel A andreceiver G. The inlet and outlet portions of the hood D are also shownat right angles to each other, as are the mouth portion of the vessel Aand the inlet portion of the receiver G. Further, the bottom of theinlet portion of the receiver G is shown in substantial alignment withthe top or lip of the mouth portion of the receiver A. As shown, thehood D provides a direct connection between the furnace vessel A and thefume processing receiver G, is of an integral, nonpartible, tubular,dual shell wall construction, is positioned for movement into acooperating fluid-sealing-ofl relation between the vessel A and thereceiver G and for movement out of such relation to permit the vessel tobe charged, tilted, repaired, etc. As shown in FIGURE 4, the hood isflexibly suspended by chains or cables in such a a manner as to centeritself into, seek and find an effective seating relation between thereceiver G and the vessel A and particularly, on the sealing edge 21::of the vessel when the sealing ring 114 of the hood is lowered into acooperating relation therewith. This eliminates the need for asectioned, refractory-lined, intermediate connection collar between avessel and its hood and whose sections are partible and swinghorizontally-outwardly therebetween.

Flame, fume, smoke, vapors, etc., are directly dischmged into the hood Dand are subjected to cooling water spray jets of suflicient intensity orforce to provide a wall-screening curtain of fluid along the innersurface of the hood D to protect it and to condition and cooldown thefume or discharge from an entering temperature of about 3000 to 3100 F.to a temperature of discharge from the hood of about 2500 F. Theintensity pressure of the spray from the jets is at least sh'ghtlygreater than the force or pressure of movement of the fume through thehood D as, for example, effected or at least partially induced by anexhaust fan (not shown) may be located within or in connection with anexhaust conduit 148 that leads from spark trap or fume receiving andprocessing apparatus G.

For an installation employing about 80 ton net converters, I havesuccessfully used spray nozzles with about a inch opening and which haveabout a 12 inch peripheral or circumferential spacing along the insideof the hood D. Such nozzles will provide jets that are of suflicientvelocity to cut through the gases or fumes when the sprays are projectedat about 120 pounds per square inch. The jet sprays not only protect theinner wall of the hood, but help to immediately solidify slag and othervaporized solids.

As shown in FIGURES 22 and 23, the discharge or outflow of fume from thehood D is flowed into the spark trap apparatus G where it is subjectedto additional cooling and conditioning action. As shown particularly inF1- URES 2a and 22, cooling fluid jets in the refractory wall of thespark trap apparatus G spray water or cooling fluid in a substantialmist form as the furne or discharge moves therethrough. Sludge andcondensed particles from the fume or discharge are collected at thebottom of the spark trap, while the now-cooled and treated gases aredischarged therefrom at a temperature of about 500 F. into the down ordischarge conduit 148 which may carry them to a final conditioningapparatus (not shown), but such as indicated in my Patent No. 2,803,450.

Referring again to FIGURES 1a and 1c, charging metal may be supplied toeach converter A by tilting it on its side and employing a chargingladle car K which moves on side tracks I On the other hand, slag may beremoved from each converter by slag cars M and refined metal by ladlecars N which operate on opposite side tracks L. It will be noted thateach converter A is mounted for tilting in opposite directions, so thatit can be easily charged, poured or tapped.

Referring particularly to FIGURES 1a, 3a, 4 and 18, the hood D is shownprovided with a top opening through which a suitable oxygen or blowlance E may project, and also through which it may be raised and loweredto, as shown in FIGURES 1a, and 2, drop it in a lance pit Q, at which itmay be cleaned or reconditioned. At the same time, a substitute lance Emay be picked-up for use. Although in FIGURES la and lo, I have shownonly one lance pit Q, it will be apparent that any number may beprovided, as needed. In this way, lances can be periodically cleaned andreused until they are worn out, at which time, they may be removed fromthe pit by an overhead crane and a new lance substituted.

The post crane apparatus B has, as shown, out-swing arm, frame or jibmeans, generally designated as C, which is moved about the central postof the apparatus B to swing it between the previously mentionedpositions I and II. T he swing arm means comprises a swing arm or jibframe 76 for raising and lowering the lance E into and out of anoperating position within the converter A (see FIGURE 4). It will benoted from FIGURES 3a and 4, that in its upper position, the lance Eclears the mouth and lip of the converter A and its lower end portionslie within the hood D. In its lower position, the end portion of thelance E is located at a suitable level with respect to the melt line,for example, with an 18 inch spacing that is suitable for the refiningoperation. In FIG- URE 4, I have shown a scale R for indicating thepositioning of the inner end portion of the lance E within the mouth ofthe converter to visually indicate it for reference and controlpurposes.

The swing arm means C also comprises a swing arm or jib frame beamstructure 52 of fixed vertical mounting with respect to the apparatus Bthat carries a swing jib or auxiliary hoist 167 for handling the lance Ewhen it is to be lowered through the hood D into a pit, such as Q. Thehoist 167' is also used when a new or replacement lance E is to belifted out of a pit Q, to be carried up into the hood D, and then to aposition above the converter A. A hood frame structure 56 carries thehood D and 'moves with it as an integral part thereof when the hood israised into and out of a sealed or cooperating relationship with theupper lip edge of the converter A, and swung into and out of positionwith the inlet flange of the spark trap G. When raised, the hood D isfree to be swung on its beam jib structure 52 out of a cooperating andsealing relationship with the entry or inlet end of the spark trap G,and to be carried with the lance E from position II to position I ofFIGURES 1a and 2. g

It should be noted that service utilities, such as water, oxygen, air,electric wiring, etc., are positioned to extend along a hollow centerpost or axis of rotation of the post crane apparatus B and along, seealso FIGURE 27, easily disconnecting swing joints, so that the apparatusincluding lmce E, may be readily connected and disconnected formaintenance and repair. In addition, flexible expansion joints areprovided to permit necessary raising and lowering movements and in thisconnection, flexible hose may also be employed. The swing joints may beof conventional construction, such as supplied under the trademarkBarco.

It will be noted that, in accordance with my invention, the converters Aare blown by means of the lances E with the hoods D tightly in place,not only with the converters A, but with respect to the spark traps G.This, with a self-centering, sealing or closing olf lance gate means125, 126 shown in FIGURES 18, and 19 to 21, substantially eliminatesaspiration of atmospheric air and nitrogen of the air during therefining operation. The construction and mounting of the hood D withrespect to each converter A is such that the hood, in effect,constitutes a top for the converter. Thus, some vaporized metal oxides,etc., may be condensed and returned to and carbon monoxide gas burned tocarbon dioxide in the converter for minimizing the loss of value contentof the melt and of the heating content of the gases. It will also benoted that the hood D has a short and abrupt-turn right-angle sideoutlet which further minimizes losses.

FIGURE 18 shows duct means F for supplying the additives, such as limeand mfll scale, through the hood D to the converter A at any time whilethe hood is in place over the converter. As previously pointed out, suchadditives may be supplied by unit P.

The raising and lowering of the swing jib 76 for the lance E may beconstructed to provide approximately 15 feet lift or movement of thelance. The raising and lowering of the swing jib for the hood may beconstructed to provide a lesser movement of about 18 to 24 inches.

As shown in FIGURES 5, 6 and 9, I have provided three drive means forthe post crane B, one 35 for rotating it as a unit along with its jibmeans C, a second 5 for raising and lowering the lance jib, and a third73 for raising and lowering the hood jib. For simplicity, electricalmotors have been utilized in this connection.

The lance E is provided with two sets or pairs of clamping means. Anupper pair or set is actuated by fiuid motor 188 (see FIGUES 14 and 15),and is carried by the lance jib 76 (see FIGURE 4) to normally grip thelance at all times when the lance is being raised and lowered by thelance jib, and except when it is to be replaced by means of theauxiliary hoist 167. A second set or pair of clamps is mounted on thevertically-fixed jib 52 of the jib means C and is actuated by fluidmotor 177 (see FIGURE 14) to grip the lance below the firstmentioned setof clamps when the lance is in its lowered position within the converterand again to aid in support ing it and to prevent pivot action when thelance is raised to its uppermost position of FIGURE 4.

Structural Details As shown particularly in FIGURES 2, 3a, 4 and 5, thefloor level of the mill has been designated as 10. Beamsupported,removable grating 10', on the same level as the floor 10, is shown inFIGURE 3a to provide easy access to operating parts of the converter A.As shown in FIGURE 2, the lance pit Q is provided by an opening in thefloor 10 that is carried on an under pit floor 9 by upright supportmembers 11. The converter A is shown mounted, at least as to itstrunnion and operating means, below the floor level on a base 12 whichcarries a pair of transversely spaced-apart trunnion stands 13 and theirassociate trunnion bearings, see particularly FIG- URES 2 and 3a.

The vessel A has, as shown in FIGURES 3 and 24, central pinion ortrunnion end shafts 14 and 14a. One shaft 14a serves as the drivethrough a speed reducing, intermeshing gear train or unit 15. The largergear of the gear unit'15 is keyed to the shaft portion 14a and the otheror smaller gear is keyed to a conventional reversible motor drive unit16, in order that the converter may be tilted or revolved to present itsmouth portion at any suitable position for charging and discharging it.

As shown in FIGURES 24 to 26, the converter A has an inner refractorylining of rounded convolute shape to correspond to the shape of thenormal wear and thus, minimize such wear particularly, during theblowing operation. The inner refractory wall 18 terminates at its upperend in a substantially vertical pour lip or mouth portion 180. Therefractory wall is of substantially the same thickness along its extent,with a slight Widening from its melt line to further increase its wearresistance. An outer metal shell or casing 19 encloses the refractorywall 18 and is reinforced by an outer frame 20 to carry the end shafts14 and 14a.

At its mouth or upper end, the vessel or converter A has a separatereinforcing framework 21 which carries an inwardly-upwardly decliningmetal sealing rim or lip portion 21a. As shown particularly in FIGURE18, it is this portion which is engaged by the sealing ring portion 114of the hood D to provide a sealing fit with respect thereto at the timeof the refining operation and of fume discharge. As shown in FIGURE 25,the converter vessel may be provided with a tap open portion 22 in itsmetal casing and a corresponding through open portion 18b in itsrefractory wall. A conventional tap hole plug (not shown) may beemployed to close off the tap hole thus provided.

In FIGURES 2, 4, and 6, I have illustrated how the post crane B issecurely bolted to the floor 10. In FIG- URE 6, it will be noted thatthe floor has suitable openings therethrough to bypass cooling water,operating air, oxygen and electrical connections. The bottom of thehoist crane B has a fixed-position or under-support frame, stand ortable 25 that extends therebeneath and carries a top or ring gear andtrack supporting plate 26. An

upwardly-projecting bull wheel or annular ring member 2'7 is secured toproject upwardly from the plate 26 and has outwardly-beveled inner ringgear or annular rack portion 27:: to mesh with a beveled drive gear,pinion or whcelZS and rotate the post crane about its central axis.

A drive shaft 29 on which the drive gear or pinion 28 is secured iscarried by bearings 39 at its ends which are suspended from an upperrotatable support frame or table structure 31. A side housing skirt orplate 32 projects downwardly from the upper support frame 31, as alsodisclosed in FIGURE 6. The drive shaft 29 has a drive Wheel gear train33 which is actuated through speed reducer 36 (see FIGURE 5) by areversible electric motor 35. The beveled gear 28 is thus driven at arelatively slow speed to advance it along the teeth of the ring gearportion 27a and effect rotation of the upper frame structure 31 aboutthe lower or stationary frame structure 26. As shown particularly inFIGURE 5, a magnetic brake 35a is provided for controlling the operationof the motor 35.

As shown in FIGURES 5 and 6, the upper frame or table structure 31 alsorotatably journals or carries a pair of beveled guide roller wheels 38that are mounted to project downwardly therefrom at an outer positionwith respect to the beveled drive wheel 25. The rollers 38 engage andmove along an outer outwardly-declining track or rail portion 27b of theannular ring member 27 for rotative movement therealong during therotation of the upper table 31.

The central portions of the stationary table 25 and the rotatable table31 are open vertically to receive a hollow central tube or post member46, along which electrical wiring, etc, are adapted to extend. The tube40 at its upper end carries an enlarged collar 41 whose lower flangeportion 41a is provided with pins 42. The limits of crane rotation maybe controlled by manual switches or by conventional electric limitswitches for the driving motor. As shown particularly in FIGURES 5 and6, the pins 42 are adapted to drop into one of several cross slots 37ain a disc ring 37 that is secured to the top of the table 31 to preventrotation of bearing housing with respect to the post crane deck. Anenlarged shaft portion 43 is secured to the collar 41 and about thecentral post or tube 49 and has bearing portions 43a to engage upon aninner bearing wall portion 31a of the rotating table 31.

The enlarged bearing shaft portion 43 terminates in a reduced lowershaft portion 44 which is engaged at its upper and lower end portions byspaced-apart guide and bearing rings 39 that are carried by an innerwall portion 25a of the bottom or stationary frame structure 25. Awasher ring 45 and end positioning nut 46 are carried on a lowermostportion of center post or tube 40 to seal ofi the above positionedbearings and hold the shaft construction in position in a fixedrelationship as to the bottom frame structure 25.

Four substantially equally-peripherally spaced-apart uprightchannel-shaped support members 50 are secured at their bottoms toproject upwardly from the upper or rotating table or frame structure 31,as shown particularly in FIGURES 5 and 6 of the drawings. A ladder 5%,see FIGURE 4, may be secured in position along one of the upright beamsor channels 5! to facilitate inspection and repair of the apparatus.

The upright support members 59 are reinforced by cross frame beams 51substantially intermediate or midway of their lengths, and at theirupper end portions, by inner portions of channel frame 52 constitute thefixed jib or outwardly-projecting support arm structure. The structureprovided by 52 has a fixed vertical positioning, but will swing or turnwith the upper table 31. As shown in FIGURE 4, the vertically-fixed jibframe or support arm structure 52 has side rails 520, so that anoperator may walk tilerealon g. The fixed jib or support arm structure52 is shown reinforced by side bracket members 53 (see FIGURES 2 and 4)which are secured at their one ends to the bottom of the fixed jib 52and at their other ends to the upright members 50.

As shown in FIGURES 2, 3a, 4 and 8, the hood D, in effect, provides onehoist jib of the post crane, sinceit is provided withupwardly-projecting lugs 58 that project from its frame 56, see alsoFIGURE 18. The lugs 58

